Where do i get bath/shower trim?

I have a problem. I was recaulking my shower pan and noticed the trim had about a 1/2" gap in it and the installers fixed that by pumping it full of caulking. I decided that was not right and tried to remove the trim, which of course broke. Now, i have no clue what its made of or where to get it! Its sort of flexible and it has flecks in it as though it were some sort of fiberglass.
Here are some pictures. The broken piece is laying there on the bench. Where do i go and where do i start looking? Whats it called? Any help is greatly appreciated. I have never done this sort of thing before.

It looks like cultured marble, and if so it was cast for your job. You really need to know who supplied it. They can make a new piece, but it might not be an exact color match because of dye lot variations.